1. Field of the Invention
The present invention relates to a method of and an apparatus for supplying a powdery material such as of a hard metal to a molten pool when forming a remelted and hardened layer on a surface of a cast iron member.
2. Description of the Prior Art
Cast iron members such as camshafts employed in internal combustion engines are required to have surface layer such as a sliding surface which is of a better wear-resistance and pitting-resistance than the rest of the cast iron member. To meet such a requirement, the applicant has proposed in a earlier application to remelt the surface layer, add powder of a hard metal to the molten pool, and chill the molten area to thereby form a hard layer that is highly resistant to wear and pit corrosion.
In the above remelting and hardening process, it is general to add the metal powder to the molten pool by supplying the metal powder through a supply tube to a burner nozzle while the metal powder is floating in dry air or an inert gas. However, the metal powder as it is supplied under the floating condition tends to be deposited on the inner wall surface of the supply tube, with the result that the substantial inside diameter of the tube is reduced, making it impossible to feed the metal powder stably. As a consequence, the metal powder is supply in irregular quantities which adversely affect the quality of the remelted members.
A conventional solution to the above difficulties has been to plate the inner wall surface of the supply tube or to construct the supply tube of a material having a low coefficient of friction. These prior measures however have failed to sufficiently prevent metal powder from being deposited on the inner wall surface of the supply tube.